Method and device for manufacturing splittable fibers and use thereof

ABSTRACT

The invention relates to a method and a device ( 2 ) for manufacturing splittable fibers ( 1 ), by means of which it is possible to conduct the melt streams of the two or more mutually incompatible polymer components (A, B) in the melt spinning process in such a way that the flow of one polymer stream around individual polymer streams, or intermingling of the various polymer streams, is prevented, in particular for greatly different weight proportions of the polymer components (A, B). 
     For this purpose, distribution holes ( 6 ) are provided upstream from at least one spinning capillary ( 4 ), and the cross-sectional area of the at least one distribution hole ( 6 ) associated with a particular polymer component (A, B) is adjusted as a function of the volumetric flow of the particular polymer component (A, B).

TECHNICAL FIELD

The invention relates to a method and a device for manufacturing splittable fibers by means of a melt spinning process, using at least two mutually incompatible polymer components, splittable fibers manufactured according to the method, and use thereof.

PRIOR ART

Methods and devices are known from EP 0 413 688, U.S. Pat. No. 5,562,930, and FR 2 647 815 for the manufacture of splittable fibers by means of a melt spinning process, using at least two mutually incompatible polymer components. The individual polymer melt streams are led through distribution plates inside a spinning head in such a way that the threads exiting the spinning head consist of multiple elementary threads of the respective polymers which, viewed in the cross section of the thread, are alternatingly positioned.

The use in particular of polyamide 6.6 as one of the polymers entails high costs for the starting material. In addition, this starting material makes it necessary to dry the raw material, generates an electrostatic charge during the spinning process, and tends to yellow under the effects of light and heat.

Therefore, there is a need to greatly reduce the proportion of one polymer component, in particular the polyamide proportion, in the splittable fibers.

By use of the known methods, however, the weight ratio of the polymer components used may be varied primarily in a proportion of 30:70 to 70:30, since otherwise, separate polymer segments are no longer obtained, and splitting into microfibers is thus difficult or even impossible.

DE 101 15 185 A1 describes a method for manufacturing splittable fibers from mutually incompatible polymer components A and B, in which the proportion of polymer component B is reduced to 5 to 25% by weight, by the fact that polymer components A and B are introduced in the molten state into a spinning head, distributed into groups of elementary threads, every other elementary thread is at least partially encased by a polymer component B, combined in spinnerets to form the splittable fibers, and subsequently drawn. Polymer component B, as the component having the lower weight proportion, thus remains as a boundary layer, i.e., a thin skin, at which separation is to be later performed.

The division of the polymer melt streams, comprising components having a lower weight proportion (minor components) and components having a higher weight proportion (major components), into numerous individual streams which together form the multicomponent fiber generally occurs directly above the spinning capillary.

For conventional spinneret packs, when the proportions of two components differ greatly from one another, the major component in the molten state often tends to flow around the other component (minor component) inside the nozzle, thus forming a closed outer shell.

On account of one of the components flowing around the other, or the components intermingling, the tendency of the otherwise incompatible polymers to split is greatly reduced. As a result, in extreme cases fibers, although composed of polymers which are actually incompatible, may no longer be splittable by mechanical means, in particular by use of water jets. In such cases the component flowing around the other may be removed, at best, by means of a solvent.

DESCRIPTION OF THE INVENTION

The object of the invention, therefore, is to provide a method and a device for manufacturing splittable fibers using a melt spinning process, by means of which it is possible to conduct the melt streams of the two or more mutually incompatible polymer components in the melt spinning process in such a way that the flow of one polymer stream around individual polymer streams, or intermingling of the various polymer streams, is prevented, in particular for greatly different weight proportions of the polymer components.

The stated object is achieved by the features of Claim 1 and Claim 15.

According to the method for manufacturing splittable fibers by means of a melt spinning process using at least two mutually incompatible polymer components, the stated object is achieved according to the invention by the fact that distribution holes are provided upstream from the at least one spinning capillary, and the cross-sectional area of the at least one distribution hole associated with a particular polymer component is adjusted as a function of the volumetric flow of the particular polymer component.

In this context, fibers are understood to mean staple fibers, continuous fibers, or filaments. Fibers that are spun into yarns are also included. The fibers may also be combined into fleeces, in particular bonded fleeces, for nonwoven fabrics.

The subclaims state advantageous refinements of the subject matter of the invention.

In one preferred embodiment of the method, the cross-sectional area of the distribution hole associated with a particular polymer component is adjusted in such a way that the flow velocities of all affected polymer components are the same, with a deviation of 0 to less than or equal to 20%, preferably less than or equal to 10%.

For this purpose, the ratio of the sum of the cross-sectional areas of the distribution holes associated with a particular polymer component to the sum of the cross-sectional areas of the distribution holes associated with another polymer component is adjusted in such a way that the ratio corresponds to the volumetric flow ratio of the polymer components used, with a deviation of 0 to less than or equal to 20%, preferably less than or equal to 10%. The volumetric flow ratio is preferably not equal to 1.

The flow velocities of all affected polymer streams are thus adjusted to be at least approximately equal, resulting in segments that are distinctly separate from one another, preferably segments having the same size cross-sectional shape, which even for the weight ratios of 80:20 to 97:3 of two mutually incompatible polymer components preferably selected for the method may be split particularly well, even using mechanical methods, in particular water jets.

As a result of the minimum proportion of less than or equal to 20%, preferably less than or equal to 15%, 10%, 5%, or 3% by weight of a component, in particular comparatively expensive polymers such as polyamide 6.6, for example, the costs for the starting materials and end products of multicomponent fibers may be reduced. Furthermore, undesired properties of a component, for example yellowing, may be reduced by use of only a minimum proportion of this component. In addition, significantly decreasing a proportion of polymer and/or the distinct segmentation of the polymer components in the fibers may also enhance the capability for recycling.

Furthermore, for a very low proportion of the minor component, when the nonwoven fabric is subsequently dyed the coloration may be limited to the major component.

In one preferred embodiment, the method is also ideally suited for a desired uniform melt distribution of polymers, in which the viscosity ratio of the polymer components is 1:1 to 10:1, preferably 1:1 to 7:1, and particularly preferably 1:1 to 4:1.

The method is also suited for the manufacture of numerous cross-sectional shapes of the multicomponent fibers.

Circular, curved, slotted, star-shaped, and/or polygonal, in particular triangular or quadrangular, cross-sectional shapes are advantageously used for the distribution holes. The distribution holes are preferably configured in a circular pattern, in particular for the manufacture of hollow fibers. Distribution holes configured in a star pattern or in a row are preferably selected.

The configurations and cross-sectional shapes of the distribution holes are preferably matched to those of the spinning capillaries.

For optimal melt flow distribution, the mutually incompatible polymer components are preferably associated with the respective distribution holes in an individually alternating or blockwise alternating manner, with the polymer components of one type preferably being associated with the respective distribution holes in equally sized blocks.

For manufacturing splittable multicomponent fibers, thermoplastic polymers selected from polyesters, preferably polyethylene terephthalate (PET), or polyolefins, preferably polyethylene (PE) and/or polypropylene (PP), or polylactates and/or polyamides (PA) are preferably used as components.

For bicomponent fibers, combinations of mutually incompatible polymer components are selected, preferably composed of PET and PP, PET and PA6, PET and PA6.6, or PP and PE.

Cost savings may be realized as a result of the lower weight proportion, in particular of comparatively expensive polymers such as polyamide 6.6.

In addition, the desired properties of the multicomponent fibers may be precisely controlled by use of specific weight proportions of the polymers used.

In a further preferred embodiment of the method, a polymer component with a lower melting temperature is preferably used as the polymer component having a lower weight proportion.

In a further preferred embodiment of the method, a polymer component having a lower weight proportion is used as adhesive or binding component. By use of these measures the properties of the nonwoven fabric thus manufactured may be influenced, and in particular the degree of bonding or softness thereof may be adjusted without the need for bonding using water jets.

The cross-sectional area of a particular distribution hole is advantageously varied by the exchange and/or addition of component parts.

The invention further relates to splittable fibers manufactured according to a method described above.

It is advantageous that the splittable fibers manufactured in particular by use of the above method, containing at least two mutually incompatible polymer components, whereby the minimum proportion of one polymer component is less than or equal to 20% by weight, preferably less than or equal to 10% by weight, particularly preferably less than or equal to 5% by weight, very particularly preferably less than or equal to 3% by weight, and the individual polymer components are composed of segments that are distinctly separate from one another, preferably comprise segments having the same size cross-sectional shape for each particular type of polymer component. It is particularly preferred to manufacture pie fibers in this manner.

The splittable fibers manufactured according to the above-referenced method are used for producing nonwoven fabrics, in particular for filters, clothing, hygienic or cleaning products, or tufted products, in particular carpet backings.

A further object of the invention is to provide a device for manufacturing splittable fibers, by means of which it is possible to conduct the melt streams of the two or more mutually incompatible polymer components in the melt spinning process in such a way that the flow of one polymer stream around individual polymer streams, or intermingling of the various polymer streams, is prevented, even for greatly different weight proportions of the polymer components. The minimum proportion of one polymer component is in particular less than or equal to 20% by weight, preferably less than or equal to 10% by weight, particularly preferably less than or equal to 5% by weight, very particularly preferably less than or equal to 3% by weight.

The object is achieved by the fact that the device has distribution holes provided upstream from the spinning capillaries, and the cross-sectional area of the at least one distribution hole associated with a particular polymer component is adjusted to the volumetric flow of the particular polymer component.

The ratio of the sums of the cross-sectional areas of the distribution holes associated with a particular polymer component preferably corresponds, at least approximately, to the volumetric flow ratio of the polymer components used, with a deviation of 0 to less than or equal to 20%, preferably less than or equal to 10%.

In one preferred embodiment of the device, the number of the distribution holes associated with a particular polymer component and the size of the cross-sectional areas of the distribution holes associated with a particular polymer component are adapted to one another in such a way that the flow velocities of all affected polymer components are essentially the same, with a deviation of 0 to less than or equal to 20%, preferably less than or equal to 10%.

Depending on the desired cross-sectional shapes of the splittable fibers to be manufactured, the distribution holes have corresponding circular, curved, slotted, star-shaped, and/or polygonal, in particular triangular or quadrangular, cross-sectional shapes.

The distribution holes are advantageously configured in a circular pattern for the manufacture of hollow fibers or filaments. Distribution holes configured in a star pattern or in a row are also provided, depending on the desired cross-sectional shape of the splittable fibers.

In one preferred embodiment of the device, the distribution holes are associated with the particular polymer components in an individually alternating or blockwise alternating manner, with the distribution holes for one type of polymer component particularly preferably being provided in equally sized blocks.

The cross-sectional area of a particular distribution hole may advantageously be varied by the exchange and/or addition of component parts.

EXECUTION OF THE INVENTION

The subject matter of the invention is explained in greater detail with reference to several examples, without limiting the invention.

The invention is described below with reference to preferred exemplary embodiments, illustrated in the drawings, of distribution holes provided upstream from the spinning capillaries, compared to a known system of a distribution plate for a spinning capillary, each of which are provided for the flowthrough of two mutually incompatible polymer components A and B in a weight ratio of 20:80 to 3:97. The drawings show the following:

FIG. 1: shows a top view of a known system and design of a distribution plate having distribution holes for a spinning capillary for the flowthrough of polymer components A (gray) and B (black);

FIG. 2: shows the flow pattern of polymer components A (solid arrow) and B (dashed arrow) by use of a known method or by use of a known device for manufacturing splittable fibers, according to FIG. 1;

FIG. 3: shows the flow pattern of the referenced polymer components A (solid arrow) and B (dashed arrow) by use of the method according to the invention or by use of the device according to the invention for manufacturing splittable fibers;

FIG. 4: shows a top view of a preferred embodiment of distribution holes configured in a circular pattern and having circular cross-sectional shapes, with different numbers of distribution holes for flowthrough of the referenced polymer components A (gray) and B (black), and in each case having the same size cross-sectional areas for flowthrough of the referenced polymer components A and B, with the total cross-sectional areas for flowthrough of the referenced polymer components A and B being different;

FIG. 5: shows a top view of one preferred embodiment of distribution holes configured in a circular pattern, having polygonal cross-sectional shapes with different numbers of distribution holes for flowthrough of the referenced polymer components A (gray) and B (black), and in each case having the same size cross-sectional areas for flowthrough of the referenced polymer components A and B, with the total cross-sectional areas for flowthrough of the referenced polymer components A and B being different;

FIG. 6 shows a top view of one preferred embodiment of distribution holes configured in a circular pattern, having circular cross-sectional shapes with the same number of distribution holes for flowthrough of the referenced polymer components A (gray) and B (black), with the cross-sectional areas for flowthrough of the referenced polymer components A and B being different, both individually and in the sum total;

FIG. 7 shows a top view of one preferred embodiment of distribution holes configured in a circular pattern and having circular cross-sectional shapes for flowthrough of the referenced polymer components A (gray), and having combined slotted and curved cross-sectional shapes for flowthrough of the referenced polymer component B (black), having the same number of cross-sectional areas for flowthrough of the referenced polymer components A and B, and with the cross-sectional areas for flowthrough of the referenced polymer components A and B being different, both individually and in the sum total;

FIG. 8: shows a perspective side view of a device according to the invention for manufacturing splittable fibers from at least two mutually incompatible polymer components A (gray) and B (black), in which distribution holes are provided upstream from the spinning capillary;

FIG. 9: shows a cross section of a fiber comprising the referenced polymer components A (gray) and B (white), manufactured by use of the method according to the invention or by use of the device according to the invention; and

FIG. 10: shows a cross section of a fiber comprising the referenced polymer components A (gray) and B (white), manufactured by use of a known method or by use of a known device.

Splittable multicomponent fibers are usually manufactured by spinning two or more polymers from spinning capillaries of a spinneret. After the fibers are spun and cooled, the individual components may be separated from one another at the interfaces of two polymer components.

FIG. 1 shows known circular distribution holes 6, configured in a circular pattern and having the same cross-sectional areas for flowthrough of mutually incompatible polymer components, for example polymer components A and B, whereby polymer components A and B are distributed over the distribution holes 6 in an individually alternating manner according to the system (AB)n, where n stands for an integer equal to or greater than 1.

On account of its greater flow velocity, polymer component B flows in a divergent manner, thereby displacing or surrounding polymer component A. This flow pattern of polymer component B (dashed arrow) and of polymer component A (solid arrow) is schematically shown in FIG. 2.

As a result, in particular for the stated weight ratios of 20:80 to 3:97, the fibers composed of polymer components A and B may no longer be splittable by mechanical means, and, if it is possible at all, may be split only by use of a solvent. However, splitting by use of a solvent is particularly disadvantageous because the solvent must subsequently be removed, and possibly recycled in a laborious procedure.

To allow mechanical splitting, in particular by use of water jets, even for fibers having greatly different weight ratios, a melt spinning method or a melt spinning device 2 is provided in which distribution holes 6 are provided upstream from the spinning capillaries 4, and in their configuration and design are specifically matched to the polymer components used.

For this purpose the cross-sectional areas of the distribution holes 6 associated with a particular polymer component are mutually adapted to the volumetric flow of the polymer components in question.

The flow velocities of all affected polymer components are set to be at least approximately equal by a corresponding adjustment of the distribution holes 6 with respect to the number of the distribution holes 6 associated with a particular polymer component and with respect to the size of the cross-sectional areas of the distribution holes 6 associated with a particular polymer component. This flow pattern is schematically shown in FIG. 3 by way of example for polymer component B (dashed arrow) and polymer component A (solid arrow).

In one preferred embodiment, the ratio of the sum of the cross-sectional areas of the distribution holes 6 associated with a particular polymer component to the sum of the cross-sectional areas of the distribution holes 6 associated with another polymer component is adjusted in such a way that the ratio corresponds, at least approximately, to the volumetric flow ratio of the particular polymer components, i.e., with a deviation of 0 to less than or equal to 20%, preferably less than or equal to 10%.

For a volumetric flow ratio of 1:4 for two polymer components A and B, distribution holes 6 of the same size, for example, i.e., having the same size cross-sectional areas, and in a number in a 1:4 ratio and having a blockwise alternating configuration A BBBB A BBBB . . . , are optimal for a uniform flow velocity of polymer components A and B through the associated distribution holes 6.

FIG. 4 shows the design of distribution holes 6 configured in a circular pattern with circular cross-sectional shapes. The ratio of the sums of the cross-sectional areas of the distribution holes 6 associated with polymer components A (gray) and B (black) is also 1:4. Polymer components A and B are associated with the particular distribution holes 6 in particular in a blockwise alternating manner.

As an alternative to the circular cross-sectional shape of the distribution holes 6, other geometries are possible, such as curved, slotted, star-shaped, and/or polygonal cross-sectional shapes.

FIG. 5 shows the design of distribution holes 6 configured in a circular pattern with polygonal cross-sectional shapes for the distribution holes 6 associated with polymer components A (gray) and B (black).

Alternatively, for a volumetric flow ratio of 1:4 for two polymer components A and B, differently sized distribution holes 6 may be used. In this case the number of distribution holes 6 associated with polymer components A and B is the same, and the size of the cross-sectional areas of the distribution holes 6 associated with polymer component B in each case is four times the size of the cross-sectional areas of the distribution holes 6 associated with polymer component A. Polymer components A and B are associated with the particular distribution holes 6 in particular in an individually alternating manner.

FIG. 6 shows the design of distribution holes 6 configured in a circular pattern with circular cross-sectional shapes.

FIG. 7 shows a top view of one preferred embodiment of distribution holes 6 configured in a circular pattern with circular cross-sectional shapes for polymer component A, and having combined slotted and curved cross-sectional shapes for polymer component B.

Of course, any other given embodiments having combinations of any volumetric flow ratios and having distribution holes 6 adapted thereto with regard to the number and size of the cross-sectional areas in any given cross-sectional shapes are also provided.

FIG. 8 illustrates a perspective side view of a device 2 according to the invention for manufacturing splittable fibers 1 from two mutually incompatible polymer components A and B, in which the distribution holes 6 are provided upstream from the spinning capillary 4. In this exemplary embodiment, the ratio of the sums of the cross-sectional areas of the distribution holes 6 associated with polymer component streams A (gray) and B (black), for a volumetric flow ratio of 1:3 for polymer components A (gray) and B (black), is correspondingly 1:3.

The distribution holes 6 shown in FIGS. 4 through 8 are optimal for a uniform flow velocity of polymer components A and B (see FIG. 3).

As a result of these embodiments, the polymer components flow in at least approximately equal flow velocities through the referenced distribution holes 6, so that multicomponent fibers 1 manufactured therefrom, with minimum proportions of one polymer component of less than or equal to 20% by weight, preferably less than or equal to 10% by weight, particularly preferably less than or equal to 5% by weight, or less than or equal to 3% by weight, have segments 8, 10 that are distinctly separate from one another, in particular having the same size cross-sectional shapes, as shown by way of example in FIG. 9 for the referenced polymer components A (gray) and B (white).

These cross-sectional shapes are particularly well suited for splitting, even by mechanical methods, in particular by use of water jets.

In contrast, the cross section of a fiber 12, shown by way of example in FIG. 10, comprising the referenced polymer components A (gray) and B (white) and manufactured by use of a known method or by use of a known device, does not have distinctly separate segments, in particular with respect to polymer component B (white). 

1. Method for manufacturing splittable fibers by means of a melt spinning process, using at least two mutually incompatible polymer components, wherein distribution holes are provided upstream from the at least one spinning capillary, and the cross-sectional area of the at least one distribution hole associated with a particular polymer component is adjusted as a function of the volumetric flow of the particular polymer component.
 2. Method according to claim 1, wherein the cross-sectional area of the distribution hole associated with a particular polymer component is adjusted in such a way that the ratio of the sums of the cross-sectional areas of the distribution holes % associated with a particular polymer component approximately corresponds to or is equal to the volumetric flow ratio of the polymer components used, with a deviation of 0 to less than or equal to 20%, preferably less than or equal to 10%, and the volumetric flow ratio is not equal to
 1. 3. Method according to claim 1, wherein the minimum proportion of one polymer component is less than or equal to 20% by weight, preferably less than or equal to 10% by weight, particularly preferably less than or equal to 5% by weight, very particularly preferably less than or equal to 3% by weight.
 4. Method according to claim 1, wherein the distribution holes are used in circular, curved, slotted, star-shaped, and/or polygonal, in particular triangular or quadrangular, cross-sectional shapes.
 5. Method according to claim 1, wherein the distribution holes are configured in a circular pattern, star pattern, and/or in a row.
 6. Method according to claim 1, wherein the mutually incompatible polymer components are associated with the respective distribution holes in an individually alternating or blockwise alternating manner.
 7. Method according to claim 6, wherein the polymer components of one type are associated with the respective distribution holes in equally sized blocks.
 8. Method according to claim 1, wherein the polymer components are selected from thermoplastic polymers, including polyesters, polyolefins, polyethylene and/or polypropylene, polylactates and/or polyamides.
 9. Method according to claim 1, wherein at least one polymer component having a lower weight proportion is used as polymer component with a lower melting temperature.
 10. Method according to claim 1, wherein at least one polymer component having a lower weight proportion is used as adhesive or binding component for manufacturing splittable fibers or filaments.
 11. Method according to claim 1, wherein the cross-sectional area of a particular distribution hole is varied by the exchange and/or addition of component parts.
 12. Splittable fibers manufactured by a method according to claim
 1. 13. Splittable fibers, manufactured by a method according to claim 1, containing at least two mutually incompatible polymer components, whereby at least one polymer component has a proportion of less than or equal to 20% by weight, preferably less than or equal to 10% by weight, particularly preferably less than or equal to 5% by weight, very particularly preferably less than or equal to 3% by weight, and the individual polymer components are composed of segments that are distinctly separate from one another, and preferably comprise segments having the same size cross-sectional shape for each particular type of polymer component.
 14. Use of splittable fibers according to claim 12 for producing nonwoven fabrics, in particular for filters, clothing, hygienic or cleaning products, or tufted products, in particular carpet backings.
 15. Device, for a method according to claim 1, for manufacturing splittable fibers from at least two mutually incompatible polymer components by means of a melt spinning process in which distribution holes are provided upstream from at least one spinning capillary, and the cross-sectional area of the at least one distribution hole associated with a particular polymer component is adjusted to the volumetric flow of the particular polymer component.
 16. Device according to claim 15, wherein the ratio of the sums of the cross-sectional areas of the distribution holes associated with a particular polymer component approximately corresponds to or is equal to the volumetric flow ratio of the polymer components used, with a deviation of 0 to less than or equal to 20%, preferably less than or equal to 10%.
 17. Device according to claim 15, wherein the distribution holes have circular, curved, slotted, star-shaped, and/or polygonal, in particular triangular or quadrangular, cross-sectional shapes.
 18. Device according to claim 15, wherein the distribution holes are configured in a circular pattern, star pattern, and/or in a row.
 19. Device according to claim 15, wherein the distribution holes are associated with the particular polymer components in an individually alternating or blockwise alternating manner.
 20. Device according to claim 19, wherein the distribution holes for one type of polymer component are provided in equally sized blocks.
 21. Device according to claim 15, wherein the cross-sectional area of a particular distribution hole may be varied by the exchange and/or addition of component parts. 